The field of the present invention is rain gauges and irrigation systems associated therewith.
Conventional irrigation controllers apply water in a pre-entered series of scheduled watering programs. A watering program or cycle is defined as a plurality of stations also called zones, each given a sequential active duration in minutes. When active, its electric solenoid valve is opened, so allowing water to its zone. The program is then given a schedule of what time of day to start its sequence and which days to water.
There frequently is an input on the controller for a switch in a sensor that is opened when a certain amount of rainfall has fallen. The opening of the rain sensor's switch pauses or cancels any running or pending watering program, so saving irrigation water when rainfall will suffice instead. There also frequently is a master valve output that is energized at the beginning of a watering program and de-energized at the end. The purpose of this output is to start an irrigation pump, or to open a common valve that supplies the network of irrigation water pipes to the individual zone solenoid valves.
The quantitative measurement of rainfall is useful in irrigation to judge how much additional water need be applied to keep a crop, golf course field or garden healthy. Various methods have been used.
The most common is a series of expanding disks that swell as they become wetted, eventually operating a micro switch. This inhibits watering by the controller until the disks dry out. Mechanical adjustments to the sensor are provided both to alter the threshold of swelling that operates the micro switch and to control the length of time it takes for the disks to dry out and shrink, so allowing watering to recommence.
Another common method is the tipping bucket. Two small buckets on a see saw, one at each end, are so positioned under the open bottom end of a collecting vessel. The higher bucket collects the rain until it tips, discarding its contents and positioning the empty bucket to collect further rain. The action of tipping activates a momentary switch, signalling that a bucket's worth of rain has been collected. The process is repeated with the other bucket and the cumulative switch closures represent the total rainfall collected. A controller can then compute the rainfall and adjust its watering durations accordingly. The assembly must be carefully adjusted to be horizontal else the amount of water in the buckets will be different before they tip.
The rain gauges employed may directly actuate the rain sensor switch of an irrigation controller. Alternatively, an adapter may be used to control the input to the rain sensor switch of an irrigation controller. Various levels of sophistication as to the quantity of water sensed, the frequency of measurement and the impact on the watering program have been provided.